[rita87]

Hello,
I have a mass spectrum but I don't know what is meant by " m* , 191 : 220 -> 205" which is wirtten on the spectrum.
220 is the MW but I don't really know what is meant by m* and 191. Can someone explain that please.

Thank you very much

[MOTOBALL]

m* 191; 220 -----> 215

This means that there is a so-called metastable ion (m*) at m/z 191. It is formed by the dissociation of the m/z 220 ion to the m/z 215 ion (loss of CH3 radical) in a field-free region of a mass spectrometer

m* = [(m2) x (m2)] / m1  where m1 -----> m2

[215 x 215]/220 = 191

Metastable ions are recognizable by their unusual shape, a somewhat broad or misshapen peak, not the usual Gaussian peak shape (symmetrical).

[MOTOBALL]

Apologies for the errors,

m* = [205 x 205]/220 = 191

It must be past my bedtime !!!!

[rita87]

Thank you very much MOTOBALL. you're a star !!!